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Re: Reduced oil temperature in reactor ?

According to a chemist here on the UK forum the weight of CaO added needs to exceed the weight of catalyst in order to combine with all the water produced in the methoxide reaction.

From memory when I prepared my dried methoxide I added 1kg of KOH to 15 litres of methanol, then added 1.5kg of CaO, mixed and left to settle 2 days. The Calcium Hydroxide formed produced a solid layer at the bottom of the container and the excess Calcium Oxide produced a layer above the CaOH2 Only this way can you be sure that all/as much water as possibe has been removed.

This does mean of course that the methoxide has to be measured into the reaction in a volumetric manner.

Re: Reduced oil temperature in reactor ?

Originally Posted by Tony From West Oz

This does not seem to be a "magic formula" for biodiesel production at room temperature.

Totally correct Tony, it is simply a way to dry the methoxide, nothing is magic, it's only chemistry. The drawback of this method I found was that using the quicklime is really messy, it flies everywhere. I used to take all the mixing gear down the field and do it there in the fresh air.

Re: The Imsides method

Last night using Imisides' idea of drying methoxide/methanol solution, I got a product at 23 degrees celcius , with fast stirring. I tested 10 milliliters of the product with 28 milliliters of methanol and got 6.1 milliliters of fall out. I meant to do the Warnquest test but remembered the proportions incorrectly. So about 13 hours later I did a 10 /90 test with crude product biodiesel and got no fall out after 1 hour. I did that reaction at room temperature here. The yellow biodiesel is hazy. I started with Magnesol treated corn oil that caused the titration number to be zero, as close as I could measure it. I dried the corn oil some by heating to over 100 C for a while, to minimize saponification, soap formation . I removed as much of the free fatty acids to minimize soap formation by reaction of base catalyst with free fatty weak acids. Fatty acids were removed with Magnesol XL and some technical grade magnesium silicate to start with as good and dry a starting material as I could. I measured the sodium hydroxide titration number of new corn oil here as 0.6 ml/litre.

Re: Reduced oil temperature in reactor ?

Totally correct Tony, it is simply a way to dry the methoxide, nothing is magic, it's only chemistry.

the two claims made for the procedure by it's inventor are:

"1. It is foolproof (no titration required)
2. It proceeds at room temperature."

While I know that there is nothing magical about processing at room temperature, on another forum I did query the inventor of the procedure why it did not require titration.
His reply was:"1. You don't need to titrate because since there is no water in the system, the concentration of FFAs no longer matters."
I am still scratching my head over that reply- maybe it is magical and FFA's are converted into biodiesel instead of soap. He never explained.

But the real magical part came later in that discussion when a fellow from your neck of the woods posted:"The method produced around 2/3 of the normal amount of glycerol (16 litres from 24litres of added methoxide) and the yield was noticeably higher, producing 208 litres of biodiesel after de-mething from 200 litres of oil."
An apparent bit of magic was going on here.
Most magical is that he used ONLY 12% methanol for the reaction. That is less than the soicheometric amount of methanol required and it is an equilibrium reaction!

Next he had a claimed yield of 104% by volume which is pretty good, especially considering he was using WVO.

To top it all off, he only produced 16 litres of "glycerol" (drop-out)
As everyone knows, there is about 74ml of glycerine in every litre of WVO
A quick calculation shows that about 14.8 litres of the 16 litres of dropout was glycerol. The dropout was about 92.5% pure glycerol!

Re: Reduced oil temperature in reactor ?

Good point Tilly; FFAs are acid. Sodium or potassium hydroxide catalyst are strong base. A neutralization reaction is acid plus base yields a salt and water. Calcium hydroxide a base or the catalyst sodium or potassium hydroxide another strong base react with free fatty acids to make the soap plus water. That's a fly in the ointment. Getting the calcium soap out is an interesting problem. The titration number of the origional vegetable oil is a factor. If the raw material was 99% free fatty acids and 1% triglyceride fatty acids, it would make a difference since almost none or zero biodiesel would be produced. But Imisides method worked at room temperature for me. I just haven't purified it yet.

I have made one modification to this method since, involving the drying agent - quicklime in Perth is nowhere near as easy to get in Perth as it was in Melb, so I had to find an alternative - and bog-standard General Purpose Grey Cement from Bunnings works just fine. Note - this is the powdered cement, not the composite with sand and aggregate in it.

In summary:

The principle behind this method is that by increasing the concentration of the catalyst I lower the activation energy (the definition of a catalyst), and this allows the process to proceed at room temperature. That means you don't have to heat it, and you can increase your batch sizes massively. i used to make it in an IBC (1000L at a time). The only mixing it required was a recirculating 550W pool pump off EBay (pump it out the bottom valve and squirt it back in the top). In winter you could hear the pump struggling a bit with the viscosity of the cold WVO, but as the reaction proceeded and the triglycerides were pulled apart you could hear the pump change pitch as the viscosity decreased.

The method has a very low tolerance for water, so your oil must be dry. I don't mean chemically dry, just no free phase water at all. I almost lost a batch when I got slack and let a bit of water in there. I managed to save it by heating it, but it's a mistake I didn't make again.

Also, I only ever dry wash. It takes about a month of bubbling an aquarium pump into an IBC to get the last of the meOH out. Then decant into 200L settling tanks with a valve right on the bottom and one about 6 inches above it. Decant from the lower valve until bio starts coming out along with the gly.

QC is I tap from the upper valve into a 500mL beaker and sit o/n. If there is any residue at all on the bottom, it's not ready and needs more time to settle.

Anyhow, it's all explained on the infopop link. I don't visit this site very often so don't expect a quick reply to any Q

Re: Reduced oil temperature in reactor ?

According to a chemist here on the UK forum the weight of CaO added needs to exceed the weight of catalyst in order to combine with all the water produced in the methoxide reaction.

From memory when I prepared my dried methoxide I added 1kg of KOH to 15 litres of methanol, then added 1.5kg of CaO, mixed and left to settle 2 days. The Calcium Hydroxide formed produced a solid layer at the bottom of the container and the excess Calcium Oxide produced a layer above the CaOH2 Only this way can you be sure that all/as much water as possibe has been removed.

This does mean of course that the methoxide has to be measured into the reaction in a volumetric manner.

I will answer this one specifiuc question. To ensure enough drying agent you just add it in excess. You can't add too much. And since a 20kg bag of cement only costs $6 I just add the whole bag, so 20kg cement to 13kg KOH. (130L 10% KOH added to 870L WVO)

In terms of the chemistry of drying agents there are two factors - capacity, and the position of the equilibrium. Some chemicals, like Na2SO4 have a massive capacity - they can suck up 10 molecules of water each (so you finish up with Na2SO4.10H2O), but the equilibrium does not lie as far to the right as MgSO4 (with a capacity of only two waters). So the organic chemist will suck up most of the water with the sodium salt and finish it off with the Mg salt. In this case you just add more drying agent than the theoretical amount (whatever it is) and the problem is solved.